Performance evaluation of bufferless optical packet switches supporting quality of service

The author evaluates the performance of bufferless optical packet switches equipped with shared tuneable optical wavelength converters (TOWC) and supporting the quality of service (QoS). The TOWCs are shared per output fibre and, hence each output fibre has a dedicated pool of TOWCs. The TOWCs are not completely shared within the node. The QoS, expressed in terms of the packet loss probability, is differentiated by giving the packets different priorities in accessing both the output wavelengths and the TOWCs. A scheduling algorithm is proposed and its complexity is evaluated. The QoS technique?s effectiveness is studied by means of an analytical model based on a probabilistic approach and validated by simulation results. The results show that the proposed technique to support the QoS facilitates a good differentiation of the QoS offered to packets.     

Numerical investigation on design of wide geographical optical-transport networks based on n/spl times/40-Gb/s transmission

We report a numerical investigation on the transmission techniques to achieve the highest capacities for n/spl times/40-Gb/s systems and such results are used to design the lightpath distribution in a European network operating with Tb/s traffic. We consider the return-to-zero (RZ) transmission assuming different pulse duration to reach the highest capacity both in the case of single-channel and of wavelength-division multiplexing. We assume the transmission in links encompassing G.652 optical fibers since they are the most installed in the world, considering the compensation of the chromatic dispersion with optical-fiber gratings. Both the amplification with erbium-doped fiber amplifier (EDFA) and hybrid Raman/EDFA is considered. We use a novel algorithm for wavelength assignment in optical networks, taking into account both the traffic requirements and the physical impairments of the networks that manifest in the signal transmission. The algorithm is based on the technique of the removing lightpaths. We report an application for a Pan European network with 26 nodes.     

Multifiber Shared-Per-Wavelength All-Optical Switching: Architectures, Control, and Performance

A new wavelength converter sharing strategy for multifiber optical switches, namely shared-per-wavelength (SPW), which employs wavelength converters with fixed input wavelengths is presented. The aim is to reduce switch costs by using simpler optical components and low complexity space switching matrices. Practical implementations of both the well-known shared-per-node (SPN) and the new SPW schemes are presented, as well as the related scheduling algorithms to manage optical packet forwarding in synchronous scenario. An analytical model to evaluate blocking performance of the SPN architecture is also provided. Results show the accuracy of the model in the range of interest for switch design. The proposed architectures are compared in terms of performance and number of optical components employed. The SPW approach is shown to save a large number of semiconductor optical amplifier gates with respect to the SPN one when the number of fibers per interface is suitably not too high. In these cases, the SPW architecture requires a number of wavelength converters higher than the SPN, but simpler, being their inputs tuned on a single wavelength.     

Resources sharing in optical packet switches with limited-range wavelength converters

This paper compares selected optical packet switching architectures that use the wavelength conversion technique to solve the packet contention problem. The architectures are equipped with shared and limited-range wavelength converters (LRWCs). This paper focuses on two architectures: the shared per node (SPN) and the shared per output fiber (SPOF) architectures, in which the wavelength converters are SPN and output fiber, respectively. Packet loss probability is expressed as a function of the number of wavelength converters used, by means of analytical models validated by simulations. The analytical results show how the use of a reduced number of LRWCs with small range allows the switch to obtain the same performances of an architecture equipped with all of the wavelength converters and using a full wavelength conversion.     

Studies based on the electrochemical response of 2-(2-nitrophenyl)-1H-benzimidazole at chemically modified electrodes with over-oxidized poly-1-naphthylamine

The development of a simple and efficient method to 2-(2-nitrophenyl)-1H-benzimidazole (NB) electrochemical determination using a polymer film coated chemically modified electrode is described. A glassy carbon (GC) electrode was modified employing an electro-polymerized film of 1-naphtylamine (1-NAP) followed by an over-oxidation treatment in 0.2 M sodium hydroxide solution (poly-1-NAPox electrode).The electrochemical behaviour of NB at the poly-1-NAPox electrode was investigated in a mixture of 10% ethanol + 90% buffer solution (pH 2) by cyclic voltammetry (CV) and square-wave voltammetry (SWV). The experimental results suggested that the poly-1-NAPox electrode had a good effect on NB electrochemical response because it avoided the electrode surface fouling as a consequence of the adsorption of NB reduction products, which was found when a bare GC electrode was employed as the working electrode. The NB cathodic current was dependent on the polymeric film over-oxidation degree (α).NB could be determined in the range from 2 × 10⁻⁶ to 5 × 10⁻⁵ M. The NB detection and quantification limits were 5 × 10⁻⁷ and 1.7 × 10⁻⁶ M, respectively. The percent relative standard deviation of the peak current to 10-replicated measurement using 1.2 × 10⁻⁵ M NB solution was 1.4%. The method showed to be rapid, simple and with a good sensitivity.     

Input wavelength conversion in optical packet switches

This letter analyzes an architecture for optical packet switches in which the wavelength converters are shared per input line (SPIL). The architecture performance are evaluated by means of an analytical model and are compared with those of an optical packet switch architecture in which the wavelength converters are shared per output line (SPOL). The obtained results show that in both balanced and unbalanced traffic scenarios the proposed architecture allows for a remarkable saving in terms of number of converters. In some cases this saving can reach 50%.     

Performance evaluation of optical cross connect architectures underan efficient wavelength assignment

In this letter we evaluate the performance of optical cross connect (OXC) architectures with wavelength conversion capability and in which the number of wavelength converters (WCs) is optimized by means of WC sharing. Dimensioning models of WCs are proposed and the number of WCs is evaluated according to an efficient wavelength assignment that allows to obtain a high saving of WCs     

Packet loss in a bufferless optical WDM switch employing sharedtunable wavelength converters

We propose an architecture for a bufferless packet optical switch employing the wavelength dimension for contention resolution. The optical packet switch is equipped with tunable wavelength converters shared among the input lines. An analytical model Is proposed in order to determine the number of converters needed to satisfy prefixed packet loss probability constraints. This analytical model very accurately fits with simulations results. A sensitivity analysis of the required number of converters as a function of the main system parameters (number of input and output lines, number of wavelengths, …) and traffic parameters has been carried out. Making use of the introduced dimensioning procedure we have observed that the proposed architecture allows a saving in terms of employed number of converters with respect to the other architectures proposed in literature. Such a saving can reach about 95% of the number of converters